This invention relates generally to an apparatus for supporting pipe sections together incident to welding the sections into a continuous length, and particularly to support units for providing local alignment of the pipe ends for tack welding.
It is frequently necessary in pipe fabrication work to weld relatively short sections of large diameter pipe together to form a continuous length. Pipes, especially those of the order of fifty inches in diameter, are commonly out-of-round to some extent and no two pipes are identical. The circumferential seam welding of large diameter, thin-walled pipes presents a problem of considerable magnitude in this respect because, when adjacent pipes are rotated on idler rolls, local misalignment of the circumferential joint margins renders accurate welding difficult. For this reason, it is desirable to tack weld the circumferential joint prior to seam welding, and some means must be provided to achieve local alignment of the pipes during the tack welding process. Elevating or lowering the pipes differentially is not a practical method of achieving this alignment.
Another problem inherent in the welding together of relatively large diameter pipes results from the desirability of having idler roll systems capable of catering to a wide range of pipe sizes. Obviously, a roll system which can easily be adapted to suit pipe diameters varying, for example, from 6 to 50 inches is a considerable advantage, but only if the adjustment can be made rapidly; without the use of expensive adjustment mechanisms and without the need for constant elevational adjustment of the pipe rotating means.
The present apparatus solves these and other problems in a manner not disclosed in the known prior art.